(i) Technical Field
The present invention relates to a hologram reading apparatus, a hologram reading method, a hologram recording apparatus and a hologram recording method.
(ii) Related Art
Some of hologram recording techniques employ the so-called coaxial-type recording technique in which a hologram recording medium is irradiated with reference light and signal light as a single beam to thereby record a hologram formed by the interference between the reference light and the signal light in the hologram recording medium. One of the advantages resulted from the employment of the coaxial-type recording technique is that the hologram recording apparatus can be miniaturized.
FIG. 5 shows a part of an optical system constituting a hologram recording/reading apparatus 2 in a related art. As shown in FIG. 5, the hologram recording/reading apparatus 2 is configured in a manner that a spatial light modulator 25 irradiates a hologram recording medium 100 with reference light and spatial-modulated signal light as the same beam to thereby record date therein. On the other hand, in the case of reading data, only the reference light serving as a reading beam is irradiated to the hologram recording medium 100 to thereby reproduce a reproduction beam, then an iris 45 shields a reference light portion of the reproduction beam and a filter 47 disposed at the focal plane of a Fourier transform lens 46 extracts a desired spatial frequency band of the signal light. A light receiving element 50 reads data based on the extracted desired spatial frequency band of the signal light.